The following describes a liquid collecting apparatus taking a blood collecting apparatus that collects blood as one example. The blood collecting apparatus is used for quantitative analyses in nuclear medicine diagnosis (e.g., PET (Positron Emission Tomography)) and so on. In the nuclear medicine diagnosis, the quantitative analyses of information on a vital function, such as concentrations of nerve receptors and metabolism of tumor, require measurement of a time variation in agent concentration of plasma in arterial blood, i.e., a radioactive concentration. The following modes are adopted in an automatic blood collecting apparatus for measuring a radioactive concentration in blood. See, for example, Patent Literatures 1 and 2, and Non-Patent Literatures 1 to 3. The apparatus are used for measuring a radioactive concentration in arterial blood of small animals (e.g., mice, rats and so on). It should be noted that the automatic blood collecting apparatus in Patent Literature 2 differs from those in the other modes in purpose of use.
[Patent Literature 1, Non-Patent Literature 1] Disclosed is a mode of introducing arterial blood flown out due to pressure of blood of a mouse itself onto a microchip (microelement) MC as illustrated in FIG. 9. The microchip MC has one main flow path FM, selectable branch flow paths FB, and a side flow path FN arranged therein. The side flow path FN flows a heparin solution H used for cleaning the flow paths and ejecting blood B or flowing out the heparin solution H and the blood B. The branch flow paths FB each include a container, and one of the flow paths is selectable depending on pressure of an argon gas G as supplied to the microchip MC and a mechanism of the microchip MC. The blood B is flown under a state where one of the branch flow paths FB is selected. Each of the flow paths FM and FB is grooved by a given size relative to the microchip MC. A length or an area of the groove into which the blood B is flown allows specification of a minute volume of the blood B. This is a characteristic of the microchip MC. With the specified minute volume, the heparin solution H is pushed under the state where the flow path is filled with a given volume of blood B, whereby the blood B is flown to a given receiver (not shown). Thereafter, each of the flow paths FM and FB is cleaned with the heparin solution H. Then the process is prepared for next blood collection. The blood B in the receiver is sucked up with physiological saline into another container, and radiation in the blood B is counted using a well counter.
[Non-Patent Literature 2] In Non-Patent Literature 2, a radiation detector is installed to sandwich a part of a catheter inserted into arteria to measure a radioactive concentration in blood. An elongated diode has a length of 30 [mm] A tube containing blood is arranged along a long side of the diode, causing an increased detectable area. This achieves ensured detection efficiency of β+-rays. The catheter includes one end connected to a syringe pump. The catheter pulls the syringe pump at a certain rate to draw blood. A flow rate of blood is calculated from the rate and a volume of blood is calculated from an internal diameter of the catheter, whereby a radioactive concentration is measured.
[Non-Patent Literature 3] As illustrated FIG. 10 in Non-Patent Literature 3, blood is returned into the vein V from the end of catheter C inserted into the arteria A. A LYSO detector D and a Perista pump P are installed in a part of the catheter C. β+-rays in the arterial blood flowing inside the interior catheter C are annihilated to generate γ-rays. The γ-rays enter into the LYSO detector D to emit light, and the number of optical fibers F is counted with the light in a collecting box B. The Perista pump P controls a flow rate of blood. A control PC calculates a volume of blood from the flow rate and the internal diameter of the catheter, thereby measuring a radioactive concentration.
[Patent Literature 2] A flow path is switched by a five-way joint to repeat ejection of blood or a cleaning liquid and collection of blood.
Patent Literature 1: Japanese Patent Publication (Translation of PCT Application) 2009-515146A
Patent Literature 2: Japanese Patent Publication No. 2001-116666A
Non-Patent Literature 1: H.-M. Wu, G Sui, C.-C. Lee, M. L. Prins, W. Ladno, H.-D. Lin, A. S. Yu, M. E. Phelps, and S.-C. Huang, “In vivo quantitation of glucose metabolism in mice using small-animal PET and a microfluidic device”, J Nucl Med, vol. 48, pp. 837-845, 2007.
Non-Patent Literature 2: L. Convert, G M. Brassard, J. Cadorette, D. Rouleau, E. Croteau, M. Archambault, R. Fontaine, and R. Lecomte, “A microvolumetric β blood counter for pharmacokinetic PET studies in small animals,” IEEE Nuclear Sci, vol. 54, no. 1, 2007.
Non-Patent Literature 3: Non-Patent Literature 2: “Blood Sampler twilite”, [online], Swisstrace, Internet URL: http://www.swisstrace.ch/blood-sampler-twilite.html